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A source S₁ is producing, 10¹⁵ photons per second of wavelength 5000 $\stackrel{\mathrm{o}}{\mathrm{A}}$. Another source S₂ is producing $1.02\times {10}^{15}$ photons per second of wavelength 5100 $\stackrel{\mathrm{o}}{\mathrm{A}}$. Then (power of S₂) to the (power of S₁) is equal to :
1. 1.00
2. 1.02
3. 1.04
4. 0.98

The potential difference that must be applied to stop the fastest photoelectrons emitted by a nickel suface, having work funcition 5.01 eV, when ultraviolet light of 200 nm falls on it, must be 
1. 2.4 V
2. 1.2 V
3. -2.4 V
4. -1.2 V

Statement 1: When ultraviolet light is incident on a photocell, its stopping potential is V₀ and the maximum kinetic energy of the photoelectrons is ${\mathrm{K}}_{\max }$. When the ultraviolet light is replaced by X-rays. both V₀ and ${\mathrm{K}}_{\max }$ increase.
Statment 2: Photoelectrons are emiited with speeds ranging from zero to a maximum value because of the range of frequencies present in the incident light
1. Both statement 1 and statement 2 are true and statement 2 is the correct explanation for statement 1
2. Both statement 1 and statement 2 are true but statement 2 not the correct explanation for statement I
3. Statement 1 is true but statement 2 is false
4. Both statement 1 and statement 2 are false

Photoelectric emission occurs only when the incident light has more than a certain minimum
1. power
2. wavelength
3. intensity
4. frequency

In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by
1. increasing the potential difference between the anode and filament
2. increasing the filament current
3. decreasing the filament current
4. decreasing the potential difference between the anode and filament

A 200 W sodium street lamp emits yellow light of wavelength 0.6 $\mathrm{\mu m}$. Assuming it to be 25 % efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is 
1. $1.5\times {10}^{20}$
2. $6\times {10}^{18}$
3. $62\times {10}^{20}$
4. $3\times {10}^{19}$

Statement 1 : Davisson-Germer experiment established the wave nature of electrons
Statement 2: If electrons have wave nature, they can interfere and show diffraction
1. Both statement 1 and statement 2 are true and statement 2 is the correct explanation for statement 1
2. Both statement 2 and statement 2 are true but statement 2 is not the correct explanation for statement 1
3. Statement 1 is true but statement 2 is false
4. Both statement 1 and statement 2 are false

The anode voltage of a photocell is kept fixed. The wavelength $\mathrm{\lambda }$ of the light falling on the cathode is gradually changed. The plate current I of the photocell varies as follows
1. 
2. 
3. \
4. 

When the energy of the incident radiation is increase by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. The work function of the metal is :
1. 0.65 eV
2. 1.0 eV
3. 1.3 eV
4. 1.5 eV

A photoelectric surface is illuminated succesively by monochromatic light of wavelength $\mathrm{\lambda } \mathrm{and} \frac{\mathrm{\lambda }}{2}$. If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface of the material is :
(h = Planck's constant, c = speed of light)
1. $\frac{\mathrm{hc}}{\mathrm{\lambda }}$
2. $\frac{2\mathrm{hc}}{\mathrm{\lambda }}$
3. $\frac{\mathrm{hc}}{3\mathrm{\lambda }}$
4. $\frac{\mathrm{hc}}{2\mathrm{\lambda }}$

An electron of mass m and a photon have same energy E. The ratio of de-Broglie wavelengths associated with them is :
1. $\frac{1}{\mathrm{c}}{\left(\frac{E}{2m}\right)}^{1/2}$
2. ${\left(\frac{E}{2m}\right)}^{1/2}$
3. $\mathrm{c}{\left(2\mathrm{mE}\right)}^{1/2}$
4. $\frac{1}{\mathrm{xc}}{\left(\frac{2m}{E}\right)}^{1/2}$
 

A particle A of mass m and initial velocity v collides with a particle B of mass $\frac{\mathrm{m}}{2}$ which is at rest. The collision is head on and elastic. The ratio of the de-Broglie wavelength ${\mathrm{\lambda }}_{\mathrm{A}}$ to  ${\mathrm{\lambda }}_B$ after the collision is 
1. 2/3
2. 1/2
3. 1/3
4. 2

Which one of the following graphs represents the variation of maximum kinetic energy $\left({\mathrm{E}}_{\mathrm{k}}\right)$ of the emitted electrons with frequency v in photoelectric effect correctly?
1. 
2. 
3. 
4. 

In a photoelectric emission, electrons are ejected from metal X and Y by light of frequency f . The potential difference V required to stop the electrons is measured for various frequencies. If Y has greater work function than X, which graph illustrates the expected results ?
1. 
2. 
3. 
4. 

A sensor is exposed for time t to a lamp of power P placed at a distance l. The sensor has an opening that is 4d in diameter. Assuming all energy of the lamp is given off as light, the number of photons entering the sensor if the wavelength of light is $\mathrm{\lambda }$ is
1. $\mathrm{N}={\mathrm{P\lambda d}}^2\mathrm{t}/{\mathrm{hcl}}^2$
2. $\mathrm{N}=4{\mathrm{P\lambda d}}^2\mathrm{t}/{\mathrm{hcl}}^2$
3. $\mathrm{N}={\mathrm{P\lambda d}}^2\mathrm{t}/4{\mathrm{hcl}}^2$
4. $\mathrm{N}={\mathrm{P\lambda d}}^2\mathrm{t}/16 {\mathrm{hcl}}^2$

The figure shows a plot of photocurrent versus anode potential for a photo sensitice surface for three different radiations. Which one of the following is a correct statement ?

1. Curves (1) and (2) represent incident radiations of same frequency but of different intensities
2. Curves (2) and (3) represent incident radiations of different frequencies and different intensities
3. Curves (2) and (3) represent incident radiations of same frequency having same intensity
4. Curves (1) and (2) represent incident radiations of different frequencies and different intensities .

A metal surface is illuminated by the light of two different wavelengths 248 and 310 nm. The maximum speeds of the photoelectrons corresponding to these wavelengths are ${\mathrm{u}}_1 \mathrm{and} {\mathrm{u}}_2$, respectively. If the ration${\mathrm{u}}_1\mathbf{:}{\mathrm{u}}_2=2\mathbf{:}1$ and hc = 1240 eV nm. The work function of the metal is nearly: 
1. 3.7 eV
2. 3.2 eV
3. 2.8 eV
4. 2.5 eV

Statement 1 :A metal surface is irradiated by a monochromatic light of frequency $\mathrm{v}>{\mathrm{v}}_0$( the threshold frequency). The maximum kinetic energy and the stopping potential are ${\mathrm{K}}_{\max } \mathrm{and} {\mathrm{v}}_0$ respectively. If the frequency incident on the surface is doubled, both the ${\mathrm{K}}_{\max } \mathrm{and} {\mathrm{V}}_0$ are also doubled.
Statement 2: The maximum kinetic energy and the stopping potential of photoelectrons emitted from a surface are linearly dependent on the frequency of incident light
1. Both statement 1 and statement 2 are true and statement 2 is the correct explanation for statement 1
2. Both statement 1 and statement 2 are true but statement 2 is not the correct explanation for statement 1
3. Statement 1 is false but statement 2 is true
4. Both statement 1 and statement 2 are false